System 3 basestation using 40MHz bandwidth?

My home wifi system management software detects a MAC address, where the sixth octet is incrementally one higher (d1) than my basestation (d0).  It is also using 40MHz bandwidth.  Is it normal for it to broadcast using two channels, say for instance, 1 & 6 or 6 & 11?  I kinda feel like I'm not only losing channel utilization, but also experiencing interference.

CB